JP3366487B2 - Stepping motor - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates are those which relate <br/> the stepping motor.

[0002]

2. Description of the Related Art In recent years, in order to reduce noise, vibration, and fine positioning of equipment, a stepping motor has been required to have a high resolution, and a microstep driving method for electrically obtaining a high resolution has been widely used. ing.

A conventional example of a PM type stepping motor will be described with reference to FIG.

In FIG. 9, 1 is a frame, 2 is a first outer yoke, 3 is a first coil bobbin, 4 is a first inner yoke, 5
Is a second outer yoke, 6 is a second coil bobbin, 7 is a second inner yoke, and 8 is an N pole and an S pole in the circumferential direction of the outer circumference of the cylindrical permanent magnet.
The rotor is magnetized in multiple poles so that the poles alternate with each other, 9 is a bracket, and 10 is a trapezoidal pole provided on each yoke so as to be parallel to the axis of the rotor 8 and face the side surface of the rotor 8. It is a tooth.

To drive the conventional example shown in FIG. 9, first,
A sine wave formed by microstep control is applied to the first coil bobbin 3, and a cosine wave formed by microstep control (a sine wave 90 ° out of phase with the sine wave) is added to the second coil bobbin 6.

A first magnetic force due to the sine wave is generated in the first outer yoke 2 and the first inner yoke 4, and the second outer yoke 5 and the second magnetic field are generated.
A second magnetic force due to the cosine wave is generated in the inner yoke 7.
Also, the pole teeth 10 of the first outer yoke 2, the pole teeth 10 of the second outer yoke 5, the pole teeth 10 of the first inner yoke 4, and the second inner yoke 7.
Pole teeth 10 are sequentially arranged at a relational position shifted by 90 ° in electrical angle, and each yoke is excited by the sine wave and the cosine wave having a phase difference of 90 ° in electrical angle. There is. Since the sine wave and the cosine wave are microstep-controlled with a phase difference of an electrical angle of 90 degrees, the N pole and the S pole of the rotor 8 are connected to the first outer yoke 2 and the first pole.
The pole teeth 10 of the inner yoke 4, the second outer yoke 5 and the second
The force received from the pole teeth 10 of the inner yoke 7 is also proportional to the waveform under microstep control, and the change in which one increases and the other decreases is repeated while reversing at an electrical angle of 90 degrees, and the rotor 8 is adjusted to the microstep control. It is driven by repeating minute rotation and stop.

[0007]

However, in the configuration of the above-mentioned conventional example, when the rotor 8 is rotated and stopped in the left and right directions, if the width of the pole teeth 10 is large, the stop position varies depending on the direction. There is a problem of hysteresis that it becomes larger, and if the width of the pole tooth 10 is large at the position where the attraction / repulsive force of the pole tooth 10 of the stator yoke and the N pole and S pole of the rotor 8 are balanced. The error becomes that much,
There is a problem that an angle accuracy error occurs. And
If the width of the pole teeth 10 of the yoke is narrowed in order to solve these problems, there arises a problem that the amount of magnetic flux decreases due to magnetic saturation and the torque decreases.

Further, for example, since the frame 1 is provided with the notch 1a for drawing out the coil wire to the outside, the magnetic circuit on the side of the first yoke and the magnetic circuit on the side of the second yoke are provided. Since the magnetic resistance is different, the magnetic flux of the magnetic circuit on the side of the second yoke having a higher magnetic resistance is smaller than the magnetic flux of the magnetic circuit on the side of the first yoke, so that the magnetic flux on the first yoke side and the magnetic flux on the second yoke side In the case of the micro-step drive, there is a problem that the collapse of the magnetic flux balance directly affects the angular accuracy and the angle accuracy is significantly deteriorated. This problem occurs not only due to the notch 1a of the frame 1, but also when there is a difference between the magnetic resistance on the side of the first yoke and the magnetic resistance on the side of the second yoke due to processing errors and other factors.

Further, the mutual inductance of the first yoke side and the mutual inductance of the second yoke side influence each other's leakage magnetic flux to generate distortion in the magnetic distribution.
In the case of the micro step drive, there is a problem in that the distortion directly affects the angle accuracy and the angle accuracy is significantly deteriorated.

[0010] The present invention is to solve the above problems, an object of Hisage <br/> subjected microstep drivable stepping motor capable of both a fact of obtaining a large torque and high angular precision .

[0011]

In order to solve the above-mentioned problems, the stepping motor of the present invention has alternating N and S poles along the circumferential direction of the outer circumference of a cylindrical permanent magnet. A stator having a multi-pole magnetized rotor, an exciting coil, and a large number of plate-shaped projecting pole teeth that constitute a magnetic circuit excited by the coil and that face the outer circumference of the rotor and are parallel to the rotor axis. In the stepping motor having a yoke, the plate-shaped protruding pole teeth have an arc shape in which the width on the base side is wide and the width on the tip side is narrow and both sides are inwardly convex.

In the stepping motor of the present invention , in order to solve the above problems, the arc-shaped radii on both sides of the plate-shaped projecting pole tooth are 2.5 times the height from the base to the tip of the pole tooth.
It is preferably 4 times.

Furthermore stepping motor of the present invention, in order to solve the above problems, section cut perpendicular to the rotor axis of the plate-like projections pole teeth, it is arc-shaped convex linear shape or rotor side It is suitable.

[0014]

In the stepping motor according to the present invention , the plate-like protruding pole teeth of the stator yoke have an arc shape in which the width on the base side is wide and the width on the tip side is narrow and both sides are inwardly convex. With this shape, even if the width of the central portion is narrowed, the width on the base side becomes wider than in the case of the conventional pole teeth of the trapezoidal plate shape. These things reduce the width of the pole teeth to improve the angle accuracy,
The width of the base side of the pole teeth is widened to prevent magnetic saturation and to prevent a decrease in torque. The radius of the arc shape on both sides was preferably 2.5 to 4 times the height of the pole teeth.

[0015] In the present invention, section cut perpendicular to the rotor axis of the plate-like projections pole teeth, the Ru arc shape der convex in a linear shape or rotor side, for each pole teeth, from the center line of the pole tooth Slip
Accordingly, the distance between the rotor and the pole teeth increases, and the magnetic flux density on the surface of the pole teeth increases near the center line and decreases as it deviates from the center line. Therefore, the width of the magnetic flux is narrowed and the angle accuracy is improved.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the PM type stepping motor of the present invention will be described with reference to FIGS.

In the present embodiment, each yoke 2 shown in FIG.
The pole teeth 10 of 4, 5, and 7 are pole teeth 10a shown in FIGS. 1 and 2 having a wide base side and a narrow tip side width, and both side edges 10b having an arcuate shape inwardly convex.

The overall structure of this embodiment is similar to that of the conventional example.
It is basically the same as that shown in FIG. 9, and the main part thereof is shown in FIG.
It is configured as shown in.

In FIGS. 2 and 9, 1 is a frame, 2 is a first outer yoke, 3 is a first coil bobbin, and 4 is a first outer yoke 2 whose pole teeth are displaced by an electrical angle of 180 degrees from each other.
The inner yoke 5 is a second outer yoke whose pole tooth position is deviated from the first outer yoke 2 by an electrical angle of 90 degrees, 6 is a second coil bobbin, and 7 is a pole tooth position which is electric with respect to the first inner yoke 4. A second inner yoke which is deviated by 90 degrees in angle, 8 is a multi-pole magnetized rotor so that N poles and S poles alternate in the circumferential direction of the outer circumference of a cylindrical permanent magnet, 9 is a bracket, and 10a is a rotor A plurality of poles having a large width on the base side and a small width on the front end side, which are provided in parallel on the side faces of the rotor 8 in parallel to the side of the rotor 8 and are parallel to the side faces of the rotor 8, have a circular arc shape in which both sides 10b are convex inward. Tooth 10a
Is. It is desirable from the experimental results that the radius of this arc shape is 2.5 to 4 times the height of the pole teeth, but it is set to 3 times in this embodiment.

By providing this arcuate shape, even if the width of the central portion is narrowed, the width on the base side becomes wider than in the case of the conventional trapezoidal pole tooth. These make it possible to reduce the width of the pole teeth to improve the angle accuracy and to widen the width of the pole teeth on the base side to prevent magnetic saturation and prevent the torque from decreasing. .

Table 1 shows the effect of improving the angle accuracy error.

[0022]

[Table 1]

In this embodiment, the number of pole teeth 10a of each yoke 2, 4, 5, 7 is 25. Therefore, in the PM type stepping motor of this embodiment, the number of all pole teeth 10a is 25 × 4 = 100, and the pole tooth angle is 360 ° / 10.
It becomes 0 = 3.6 degrees (90 degrees in electrical angle). Since the number of steps (the number of pulses) corresponding to the electrical angle of 90 degrees (physical angle of 3.6 degrees) of the micro step sine wave to be used is 80, one step is 3.6 degrees / 80 = 0.04.
It will be 5 degrees. Table 1 shows that the conventional example has an angle accuracy of 0.04.
It is 6.24 times 5 degrees, but in this embodiment, it is 3.18 times.

In FIG. 2, the pole teeth A of the first outer yoke 2, the pole teeth B of the first inner yoke 4, the pole teeth C of the second outer yoke 5, and the pole teeth D of the second inner yoke 7 are excited. Have a relationship as shown in Table 2.

In Table 2, N (N pole) → O (neutral) indicates that the magnetic flux gradually changes from the N pole state to the neutral state in 80 steps, and O → S, S.
→ O and O → N have the same meaning.

[0026]

[Table 2]

FIG. 3 is a comparison of the torques of this embodiment and the conventional example, showing that even if the frequency becomes high, the torque does not decrease so much that both the angle accuracy and the torque can be achieved. There is.

Second PM type stepping motor of the present invention
An embodiment will be described based on FIGS. 4, 5, and 9.

FIG. 4 shows each yoke 2 used in this embodiment.
In the plan views of 4, 5, and 7, the shape of the pole tooth 10c viewed from above is shown. The pole teeth 10c have both sides 10 when viewed from the front.
d and 10d are linear shapes, which are similar to the conventional trapezoidal plate shape, but as shown in the plan view of FIG. 4, a cross section cut perpendicular to the rotor axis has an arc shape 10e convex toward the rotor axis side. Has become. In the present embodiment, the radius of the arcuate shape 10e is set to be the same as the outer diameter radius of the rotor 8, but the present invention is not limited to this and can be set freely as long as it is convex inside. Alternatively, it may be a straight line.

In the conventional PM type stepping motor,
In FIG. 9, since the distance between the rotor 8 and the pole teeth 10 is equal in the entire width of the pole teeth 10, the magnetic flux densities at the respective positions on the entire surface of the pole teeth 10 are substantially the same, whereas In the embodiment, for each pole tooth 10c, the distance between the rotor 8 and the pole tooth 10c becomes large at a position displaced from the center line of the pole tooth 10c, and the magnetic flux density on the surface of the pole tooth 10c is near the center line. Is large, and becomes smaller as it deviates from the center line, the spread of the magnetic flux distribution is reduced, and the angle accuracy is improved.

[0031]

[Table 3]

Table 3 shows a comparison of angular accuracy between this embodiment and the conventional example. In FIG. 4, the number of pole teeth 10c is 12 for convenience of drawing, but the actual number is 25, which is the same as in the first embodiment. Table 3 shows that in the conventional example, the angle accuracy is 0.
Although it is 6.24 times 045 degrees, it is 4.58 in this embodiment.
It shows that it doubles.

FIG. 5 is a comparison of the torques of this embodiment and the conventional example, showing that even if the frequency becomes higher, the torque is less likely to decrease and the angle accuracy and the torque can both be achieved. There is.

A third embodiment of the stepping motor driving method of the present invention will be described with reference to FIG.

In this embodiment, the conventional PM type stepping motor shown in FIG. 9 has a phase difference of 8 as shown in FIG.
It is a constant voltage drive in which two microstep sine wave voltages of 3 degrees are applied to the two coils 3 and 6. According to experiments, it is desirable that the phase difference is in the range of 60 degrees to 88 degrees.

[0036]

[Table 4]

Table 4 shows a comparison of angular accuracy between this embodiment and the conventional example. In this embodiment, the number of pole teeth 10 of one yoke is 25, which is the same as in the first embodiment. Table 4 shows that in the conventional example, the angle accuracy is 6.45 times 0.045 degrees, but in the present embodiment, it is 3.96 times.

In this embodiment, constant voltage driving is used, but constant current driving is also the same.

A fourth embodiment of the stepping motor driving method of the present invention will be described with reference to FIG.

In the present embodiment, as shown in FIG. 7, a microstep sawtooth wave voltage is applied to a coil having a low magnetic resistance and a microstep sine wave is applied to the other PM type stepping motor shown in FIG. Applying voltage. The phase difference between the two waveforms is 90 degrees.

[0041]

[Table 5]

Table 5 shows a comparison of angular accuracy between this embodiment and the conventional example. In this embodiment, the number of pole teeth 10 of one yoke is 25, which is the same as in the first embodiment. Table 5 shows that in the conventional example, the angle accuracy is 6.45 times 0.045 degrees, but in the present embodiment, it is 4.98 times.

In this embodiment, constant voltage driving is used, but constant current driving is also the same.

A fifth embodiment of the stepping motor driving method of the present invention will be described with reference to FIG.

In the present embodiment, as shown in FIG. 8, a PM stepping motor of the conventional example shown in FIG. 9 is applied with a microstep sine wave voltage of a maximum value of 5 V to the coil on the lower magnetic resistance side, and the other is applied to the other. A microstep sinusoidal voltage with a maximum value of 6V is applied. The phase difference between the two waveforms is 90 degrees.

[0046]

[Table 6]

Table 6 shows a comparison of the angle accuracy between this embodiment and the conventional example. In this embodiment, the number of pole teeth 10 of one yoke is 25, which is the same as in the first embodiment. Table 6 shows that in the conventional example, the angle accuracy is 6.45 times 0.045 degrees, but in the present embodiment, it is 4.16 times.

In this embodiment, constant voltage driving is used, but constant current driving is also the same.

The present invention is not limited to the above embodiment, but may be a combination of the characteristic parts of the first and second embodiments, for example. The first embodiment, the second embodiment, or the combination of the first embodiment and the second embodiment,
It is also possible to combine any of the characteristic portions of the third to fifth embodiments.

[0050]

As described above, the stepping motor of the present invention has an effect that both the improvement of the angle accuracy error and the avoidance of the torque decrease due to the magnetic saturation can be achieved .

[Brief description of drawings]

FIG. 1 is a front view of pole teeth of a first embodiment of a stepping motor according to the present invention.

FIG. 2 is a partially exploded perspective view of the first embodiment of the stepping motor of the present invention.

FIG. 3 is a diagram showing a comparison between the torque characteristic of the first embodiment of the stepping motor of the present invention and the torque characteristic of the conventional example.

FIG. 4 is a plan view of a stator yoke of a second embodiment of the stepping motor of the invention.

FIG. 5 is a diagram showing a comparison between the torque characteristic of the second embodiment of the stepping motor of the present invention and the torque characteristic of the conventional example.

FIG. 6 is a third step of the driving method of the stepping motor according to the present invention.
It is a figure which shows the voltage waveform used in an Example.

FIG. 7 is a fourth method of driving a stepping motor according to the present invention.
It is a figure which shows the voltage waveform used in an Example.

FIG. 8 is a fifth step of a method for driving a stepping motor according to the present invention.
It is a figure which shows the voltage waveform used in an Example.

FIG. 9 is a diagram showing a general configuration of a stepping motor.

[Explanation of symbols]

1 frame 1a cutout 2 First outer yoke 3 First coil bobbin 4 First inner yoke 5 Second outer yoke 6 Second coil bobbin 7 Second inner yoke 8 rotor 9 bracket 10 pole teeth 10a pole teeth 10b side 10c pole teeth 10d side

Front page continued (58) Fields surveyed (Int.Cl. ⁷ , DB name) H02K 37/00-37/24 H02K 1/00-1/34 H02K 21/00-21/48

Claims (3)

(57) [Claims] 1. A rotor, which is multi-pole magnetized so that N poles and S poles alternate along the circumferential direction of the outer circumference of a cylindrical permanent magnet, a coil for excitation, and an excitation by the coil. And a stator yoke having a large number of plate-shaped protruding pole teeth facing the outer circumference of the rotor and parallel to the rotor axis, the plate-shaped protruding pole teeth having a width on the base side. The stepping motor is characterized by an arc shape in which the width is wide and the width at the tip side is narrow and both sides are convex inward. 2. The stepping motor according to claim 1, wherein the arc-shaped radii on both sides of the plate-shaped protruding pole tooth are 2.5 to 4 times the height from the base to the tip of the pole tooth. 3. The stepping motor according to claim 1 , wherein a cross section of the plate- like projecting pole teeth cut perpendicularly to the rotor axis has a linear shape or an arc shape convex toward the rotor side.